1. Field of the Invention
The present invention relates to the field of optical analysis of fluid streams and, in particular, to flow-type particle analyzers, such as flow cytometers, and particle sorting systems.
2. Description of Related Art
Flow-type particle analyzers, such as flow cytometers, are well known analytical tools that enable the characterization of particles in a fluid stream on the basis of optical parameters such as light scatter and fluorescence. In a flow cytometer, particles such as molecules, analyte-bound beads, or individual cells in a fluid suspension are passed by one or more detectors in which the particles are exposed to an excitation light, typically from one or more lasers, and the light scattering and fluorescence properties of the particles are measured. Each particle, or subcomponents thereof, may be labeled with a multiplicity of spectrally distinct fluorescent dyes. Typically, detection or characterization is carried out using a multiplicity of photodetectors, one for each distinct dye to be detected.
Flow-type particle sorting systems, such as sorting flow cytometers, are used to sort particles in a fluid sample based on the characterization of the particles. In a flow-type particle sorting system, the fluid stream is jetted from a nozzle and a droplet generator vibrates fluid stream to break the stream into uniform discrete drops after optical analysis. When a particle of the type to be sorted is detected, a sorting mechanism is triggered to separate the drop containing the particle from the stream of drops. A number of methods of sorting particles are known in the art, including the use of moving droplet capture tubes (as described in U.S. Pat. No. 5,030,002) and electrostatic sorting. In electrostatic sorting, drop charging means are connected to the stream to charge drops containing a particle of the type to be sorted with an electrical charge as it breaks off from the jet stream. The stream of drops is passed through a transverse electrostatic field established by a pair of oppositely charged deflection plates. Uncharged drops are not deflected passing through the electrostatic field and are collected by a central receptacle. Charged drops containing a particle of the type to be sorted are deflected in a direction and amount related to the polarity and magnitude of the drop charge and are collected in a separate collection receptacle.
Optical analysis of particles using a sorting flow cytometer typically is carried out after the stream has been jetted from the nozzle. Alternatively, the analysis is carried out while the fluid stream is passing through a channel in an optical cuvette, as is typically used in an analyzing flow cytometer. Sorting flow cytometers that use a cuvette for optical analysis are described in, for example, U.S. Pat. Nos. 4,660,971 and 7,201,875; the entire contents of both patents incorporated herein by reference.
Flow cytometers and sorting flow cytometers are described in Shapiro, 2003, Practical Flow Cytometry (John Wiley and Sons, Inc. Hoboken, N.J.); and “Flow Sorters for Biological Cells” by Tore Lindmo, Donald C. Peters, and Richard G. Sweet, Flow Cytometry and Sorting, 2d ed. (New York: Wiley-Liss, Inc., 1990), pages 145-169, both incorporated herein by reference. Flow cytometers and sorting flow cytometers are commercially available from, for example, BD Biosciences (San Jose, Calif.).
In a number of applications in flow cytometry, such as sorting of cells for therapeutic use, it is desirable to sterilize or replace the fluidic path after each use. Replacement of the components of the fluidic path typically requires realignment of the excitation and detection optics, which is both time-consuming and difficult.